Fluorocarbon based fluids have found widespread use in industry in a number of applications, including as refrigerants, aerosol propellants, blowing agents, heat transfer media, and gaseous dielectrics. Because of the suspected environmental problems associated with the use of some of these fluids, it is desirable to use fluids having low or even zero ozone depletion potential, such as hydrofluorocarbons (“HFCs”) and hydrochlorofluorocarbons (“HCFCs”).
As is known, fluorochemicals are frequently included as a component in blowing agents utilized in the manufacture of various synthetic plastic formed products. For many years CFC-11 was a very important product in this market. In recent years, however, CFC-11 has frequently been replaced by the bridge-fluorocarbon HCFC-141b. More recently, a need has arisen (caused at least in part by government regulation) for foam manufacturers to discontinue use of the HCFC-141b by the end of the year 2003 in favor of even more desirable HFC products.
One HFC, which has become commercially important as a replacement for environmentally deficient products, such as HCFC-141b, is the HFC 1,1,1,3,3-pentafluoropropane (“HFC-245fa”). Many processes for producing HFC-245fa involve the use of the HCC 1,1,1,3,3-pentachloropropane (“HCC-240fa”) as a reactant. For example, U.S. Pat. No. 6,023,004, which is assigned to the assignee of the present invention and which is incorporated herein by reference, describes the liquid phase catalytic fluorination of 1,1,1,3,3-pentachloropropane to HFC-245fa.
Thus, because of the importance of HFC-240fa as a feedstock in the production of HFC-245fa, improvements in the processes used to produce HCC-240fa can have a positive impact on the development of HFC replacements for products, which are not environmentally desirable.
U.S. Pat. No. 6,313,360 describes a process for producing HCC-240fa by first reacting carbon tetrachloride (CCl4) and vinyl chloride in the presence of a catalyst mixture comprising organophosphate solvent, iron metal and ferric chloride under conditions sufficient to produce a product mixture containing HCC-240fa. The product mixture is then fractionated such that a tops fraction enriched in HCC-240fa is separated from the product mixture and a bottoms fraction results, which comprises the iron metal/ferric chloride catalyst components and heavy end by-products. A portion of the bottoms fraction is recycled to the reactor. Other processes produce similar reaction product streams.
Because carbon tetrachloride is a reactant in such processes, it is common that the reaction product mixture will contain HCC-240fa and carbon tetrachloride. These components typically will be contained in a light fraction from one or more of the fractionation steps described in the prior art. As described in detail hereinafter, applicants have discovered that certain combinations of HCC-240fa and carbon tetrachloride exhibit the unique and unpredictable property of azeotropy, and applicants have therefore come to appreciate a need for improved processes directed specifically to the production of HCC-240fa and/or HFC-245fa. In addition, IICC-240fa may be present as a reaction product in many fluorination reactions directed to the production of other fluorinated compounds. Thus, applicants have come to appreciate and need more generally for improved processes directed to the production of HFCs and HCFCs.